1. Field of the Invention
The present invention relates to a low-frequency voltage sensor and more particularly to a stress-driven low-frequency electrostrictive ceramic plate voltage sensor.
2. Description of the Related Art
Field response materials, e.g., magnetostrictive metals and electrostrictive ceramics, are used in sensors.
The measurement of low-frequency magnetic fields utilizing a magnetoelastic amorphous metal low-frequency magnetic field sensors with a magnetostrictive amorphous metal ribbon has been discussed by Mermelstein in the paper entitled A Magnetoelastic Metallic Glass Low-Frequency Magnetometer, IEEE Trans. Magn. Vol. 28, No. 1, pp. 36-56, January 1992. This technique is based upon the magnetoelastic interaction between the magnetization and strain in field-annealed amorphous metal ribbons. The magnetoelastic magnetometer has the ability to measure the low-frequency magnetic field and magnetic field gradiants in the presence of other low-frequency perturbations such as temperature and other stress fluctuations.
The principle of operation of the magnetometer is based upon the field-dependent coupling between the magnetization and strain modes in the magnetostrictive amorphous material. It is constructed by interfacing a resonating piezoelectric plate to a field-annealed magnetostrictive amorphous ribbon with a viscous fluid. The piezoelectric plate serves to generate a well-defined stress wave in the ribbon at acoustic frequencies where the viscous fluid transfers the strain in the ceramic to the ribbon.
Also, electrostrictive ceramics have been demonstrated for use in the detection of low-frequency voltages in fiber optic interferometers, as discussed in the paper Fiber-optic dc and low-frequency electric field sensor, Vohra et al., Opt. Ltrs., Vol. 16 No. 18, pp. 1445-1447, September 1991. However, they require the use of fiber-optic interferometers to measure low-frequency voltages. Presently, this is the only technology available to measure low-frequency voltages using electrostrictive materials.